Among print systems for printing on print mediums, an ink jet system is known which ejects ink from a print head as a print means onto the print medium to print an image. Such an ink jet system has many advantages, such as an ability to reduce a size of the print head easily, an ability to form highly defined images at high speed, a low running cost made possible by the ability to print on even so-called plain paper, small noise achieved by a non-impact system, and an ease with which to employ a construction for making color images using multiple color inks.
Because of these advantages, the ink jet printing apparatus have found a wide range of applications in industries, offices and homes (for personal and family use), and the printing purposes have also diversified widely. A variety of kinds of print mediums are available for use. In industrial fields, in particular, a wide range of medium size, from a relatively small one such as labels stuck to products and their packages to a relatively large one, for instance A2-size or greater, is being used. Demands on the printing apparatus used in industrial fields are far more stringent than those of personal use in terms of faster printing speed and operation stability.
Patent document 1 describes a serial printing system. This printing system forms an image by moving a print head along the print medium (main scan) and, after each main scan, feeding the print medium a predetermined distance (sub scan) and then repeating this process. In contrast to this printing system, a line printer type printing system uses a print head having a large number of ink ejection nozzles arrayed in a direction perpendicular to the direction in which the print medium is fed (sub scan direction). The line printer type can form an image at a faster speed and therefore is drawing attention as a suitable printing apparatus for industrial use.
In industrial fields, however, various sizes of print mediums are used as described above and at times the printer may have to print on a large print medium as A2-size or more. In a print head applied to the line printer in particular, it is difficult to form a very large number of nozzles over the entire width of a print area without any defect (unless otherwise specifically noted, a word “nozzle” generally refers to an ink ejection opening, an ink path communicating with the ink ejection opening or nozzle opening, and an element arranged in the ink path to generate an ink ejection energy). Suppose, for example, the print width on an A2-size print medium is about 420 mm (on a short side of A2 size) and that the printing is performed at 600 dpi. Then, about 10,000 nozzle openings are required in this print width. Forming such a large number of nozzles corresponding to the nozzle openings without a defect not only makes manufacturing equipment large in scale but also reduces a yield, rendering the production extremely costly.
Under these circumstances, it is a conventional practice to manufacture a line printer ink jet print head of a desired length by arranging a plurality of relatively inexpensive, short print head chips in line with high precision (e.g., patent document 2). By arranging an appropriate number of print head chips in line as described above, it is possible to deal with various sizes of print mediums.
The information processing device as a host apparatus to supply image data to the printing apparatus has its image data development and transfer system constructed to conform to the construction of the printing apparatus, particularly the number of nozzles and the arrangement of nozzles and print head chips (e.g., patent document 1). Image data created by the user is supplied to the printing apparatus via a communication interface.    Patent document 1: Japanese Patent Laid-Open No. 2001-171140    Patent document 2: Japanese Patent Laid-Open No. 60-137655